I found my answer, I just needed to add IsHitTestVisible="False" to the overlay Border. I didn't realize this would be necessary in this scenario, but it fixed the problem, so I guess it has the title of Answer!
Drag & Drop For Elements Underneath A Border
Nathan Sokalski
4,111
Reputation points
I have a Border with Background="#50FFFFFF". As you will notice, the A component (the opacity) of the color is less than 255, making the Border partially see-through. I use this Border to lighten the appearance of several elements underneath it (this was much easier than modifying the details of all the other controls & their Styles). However, it prevents me from using Drag & Drop to drop elements onto the elements underneath it. Is there any way to allow the Drag & Drop events (such as DragEnter) to be detected by the elements underneath the Border? Thanks.